This invention is directed to a new and improved method of manufacturing an amorphous metal composite composite. In particular, this invention relates to a new and improved method of making an amorphous metal composite comprising amorphous iron and a suitable thermosetting polymer binder. In general, the new and improved method of the present invention comprises placing an amorphous metal in particulate form (e.g., flakes or filaments) and a thermosetting polymer binder powder into a container; mixing these materials, and applying heat and pressure to convert the mixture into an amorphous metal composite made by the method. The resulting amorphous metal composite of the present invention may be utilized in motor stators providing increased electric motor efficiency and opportunities for innovative electric motor designs.
Amorphous iron alloys have great potential for use in many types of electrical devices because of their unusual magnetic properties. In order to take advantage of these properties it is necessary that the alloy be fabricated into 3-dimensional structures. Conventional casting techniques have been utilized in fabrication of the 3-dimensional structures. However, the structures produced by these conventional techniques have been found wanting because the quench rates are much too slow resulting in crystallization of the alloy. This crystallization destroys the amorphous nature of the alloy. Therefore, the unusual magnetic properties attributed to the composite alloy because of its amorphous characteristics are also destroyed.
Quenching techniques utilizing rotating wheels mounted in water baths are capable of producing amorphous metal ribbons which are 0.5-2 mils thick and usually under 2 inches wide. However, to fabricate parts from these ribbons, it is necessary that they be coated with a binder and pressed to produce laminated articles. This procedure is time consuming and expensive.
Recently, it has been discovered that new production techniques have yielded amorphous metal flakes or filaments possessing the same magnetic properties present in the ribbons. This discovery has been used in various attempts to develop new and improved articles and processes where these amorphous metal flakes or filaments can be used to fabricate bulk molded parts possessing the high packing factor necessary for good electronic and power devices. The term packing factor is defined as the total volume of metal flake or filament over the total volume of the resulting molded part. A high packing factor is desired because the properties of the molded part should approach the properties of the amorphous metal flakes or filaments themselves. Experiments by applicants were initially directed to the use of epoxy resins as the binder for the amorphous flakes or filaments. Epoxy resins were selected because of their generally recognized properties of good adhesion to metal substrates. However, the experiments with these materials have led applicants to the conclusion that epoxy systems are not suitable as binders for the amorphous metal composite because (1) the resulting composite possesses an extremely low packing factor, and (2) epoxy binders are not capable of enduring the required high temperature annealing treatment (e.g. 300.degree. C.).
In addition, applicants experimented with commercially available polymides and polyamideimides which are known to exhibit excellent thermal life at elevated temperatures. For example, DuPont NR-150 which is a polyimide precursor solution based on 2,2-bis-(3,4-dicarboxyphenyl) hexafluoropropane and mixtures of 4,4 oxydianiline (ODA) and p-phenylenediamine (PPD), and AI600, a polyamideimide manufactured by General Electric are useful binders for laminates of the amorphous ribbon segments mentioned previously. The use of these types of polymer solutions for the production of coated flakes or filaments made the attainment of the proper B-staging of the binder on the flake quite cumbersome and impractical. These same polymers, when utilized as dry powders, possessed adequate high temperature capability but lacked the melt flow characteristics needed to wet the flakes or filament during the molding operation.
Accordingly, the discovery of a suitable binder which can (1) withstand the high annealing temperatures, (2) possess suitable wet flow characteristics needed to wet the flakes or filament during molding, and (3) permit the resulting composite to obtain a high packing factor has not been made until the present invention.